This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Diabetes mellitus is recognized as a leading cause of new cases of blindness among Americans between the ages of 20 and 74. In comparison with the general population, diabetic patients face a 25-fold increased risk of blindness. Our long term objectives are to elucidate mechanisms involved in diabetic eye disease in order to develop strategies to prevent or delay the devastating effects of diabetes on the eye. Aldose reductase has been implicated in the pathogenesis of diabetic cataract and retinopathy, but we do not understand the mechanism. The goals of this project are to determine whether the onset and progression of diabetic eye disease is influenced by genetic manipulation of aldo-keto reductase enzyme levels. Specific aim one will test the hypothesis that diabetic cataract formation is not dependent on production of sugar alcohols by aldose reductase. This will be accomplished with the use of transgenic mice that direct lens expression of either aldose reductase, which catalyzes conversion of glucose to sorbitol, or small intestine reductase, which does not catalyze glucose-dependent sorbitol synthesis. Consequences of transgene expression will be assessed with and without induction of experimental diabetes. Transgenic lenses will be studied for accelerated lens epithelial cell apoptosis and diabetes-induced alterations of epithelial cell morphology. Biochemical markers of oxidative stress will also be measured. Specific aim two will test the hypothesis that deletion of genes for aldose reductase and related aldo-keto reductases will protect against diabetic retinopathy and cataract. Morphological and functional changes to retinal vascular cells following induction of experimental diabetes will be assessed in gene knockout and control mice. Measurement of apoptotic vascular cells in different lines of gene-targeted mice will reveal whether aldo-keto reductase gene expression contributes to the pathogenesis of diabetic retinopathy. Similar comparisons will be made for lens transparency to determine the influence of individual AKR genes on diabetic cataract.